Modeling shape selection of buckled dielectric elastomers

TL;DR

This paper develops a numerical model to study buckling shapes of fixed-edge dielectric elastomers under voltage, validating it against experiments and exploring multiple equilibrium configurations.

Contribution

It introduces a simplified nonlinear elastic model incorporating electrostatic stresses and applies a deflation technique to find multiple equilibrium shapes.

Findings

Model accurately predicts axisymmetric buckling shapes.

Annular electrodes produce ripples matching simulations.

Multiple equilibrium solutions are essential for certain geometries.

Abstract

A dielectric elastomer whose edges are held fixed will buckle, given sufficient applied voltage, resulting in a nontrivial out-of-plane deformation. We study this situation numerically using a nonlinear elastic model which decouples two of the principal electrostatic stresses acting on an elastomer: normal pressure due to the mutual attraction of oppositely charged electrodes and tangential shear ("fringing") due to repulsion of like charges at the electrode edges. These enter via physically simplified boundary conditions that are applied in a fixed reference domain using a nondimensional approach. The method is valid for small to moderate strains and is straightforward to implement in a generic nonlinear elasticity code. We validate the model by directly comparing the simulated equilibrium shapes with the experiment. For circular electrodes which buckle axisymetrically, the shape of the deflection profile is captured. Annular electrodes of different widths produce azimuthal ripples with wavelengths that match our simulations. In this case, it is essential to compute multiple equilibria because the first model solution obtained by the nonlinear solver (Newton's method) is often not the energetically favored state. We address this using a numerical technique known as "deflation". Finally, we observe the large number of different solutions that may be obtained for the case of a long rectangular strip.